Keratometry, biometry and prediction of intraocular lens power in the equine eye.
Abstract: To determine ocular dimensions (A- and B-scan ultrasound) and corneal curvature (radius of corneal diameter determined in B-scan ultrasound) in the equine eye and to calculate the appropriate dioptric power for a posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of horses undergoing lens extraction. Methods: Fourteen clinically normal adult horses of various breeds. Additionally, for comparison, one American Miniature colt foal, and one 2.5-year-old Shire gelding were examined. Methods: B-scan ultrasound was performed on one eye from each horse. One eye from both the Shire and the American Miniature were examined for comparison. Data from ultrasound (globe measurements and corneal curvature), and the estimated postoperative IOL positions were entered into theoretical IOL formulas (Binkhorst and Retzlaff theoretical formulas) in order to calculate the predicted IOL strength required to achieve emmetropia after lens extraction in horses. Results: Mean axial length of globes was 39.23 mm +/- 1.26 mm, mean preoperative anterior chamber depth (ACD) was 5.63 +/- 0.86 mm, and mean lens thickness was 11.75 +/- 0.80 mm. Predicted postoperative ACD (PACD) was calculated as the ACD plus 50% of the lens thickness. Additionally, PACD 2 mm anterior and 2 mm posterior to the center of the lens were calculated in order to evaluate the effect of IOL position on its required refractive power. Required IOL strength calculated, using the three values for the predicted postoperative ACD, was 29.91 D +/- 2.50, 29 D +/- 2.52 (center of lens); 27.13 D +/- 2.27, 26.33 D +/- 2.20 (2 mm anterior to center of lens); and 33.18 D +/- 2.78, 32.24 D +/- 2.68 (2 mm posterior to center of lens) with the Binkhorst and Retzlaff theoretical formulas, respectively. Conclusions: An IOL of substantially lower diopter strength than that needed in either dogs or cats is required to achieve emmetropia after lens extraction in adult horses. IOL strength of approximately 30 D, depending on where the IOL ultimately comes to rest, will probably be required.
Publication Date: 2006-08-31 PubMed ID: 16939465DOI: 10.1111/j.1463-5224.2006.00493.xGoogle Scholar: Lookup
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- Evaluation Study
- Journal Article
Summary
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This research paper is about finding the right intraocular lens (IOL) replacement for horses undergoing lens extraction surgery. It considers factors like the eye’s dimensions, corneal curvature and the postoperative position of the lens to calculate the right IOL strength.
Objective of the Research
- The purpose of this study is to investigate the necessary parameters to determine the correct dioptric power for a posterior chamber IOL to achieve emmetropia (a condition where the eye can focus images correctly on the retina) in horse eyes undergoing lens extraction.
Methodology
- The study used fourteen adult horses of various breeds as the primary subjects. For comparison purposes, they also examined the eyes of an American Miniature colt foal and a 2.5-year-old Shire gelding.
- Researchers performed B-scan ultrasounds on one eye from each horse to gather data about globe measurements and corneal curvature.
- The estimated postoperative IOL positions were then entered into theoretical IOL formulas (Binkhorst and Retzlaff theoretical formulas), to compute the predicted IOL strength required to achieve emmetropia.
Results
- The study found the mean axial length of globes was 39.23 mm, mean anterior chamber depth (ACD) was 5.63 mm, and mean lens thickness was 11.75 mm.
- They calculated the predicted postoperative ACD as ACD plus 50% of the lens thickness. Also, PACD 2 mm anterior and 2 mm posterior to the center of the lens were computed to ascertain the effect of the IOL position on its required refractive power.
- The necessary IOL strength computed using the three values for the predicted postoperative ACD showed that substantially lower diopter strength than that needed in either dogs or cats is necessary to achieve emmetropia in adult horses.
Conclusions
- The study concluded that an IOL strength of approximately 30 D will likely be needed, depending on where the IOL ultimately comes to rest, to attain emmetropia in horses post lens extraction surgery.
Cite This Article
APA
McMullen RJ, Gilger BC.
(2006).
Keratometry, biometry and prediction of intraocular lens power in the equine eye.
Vet Ophthalmol, 9(5), 357-360.
https://doi.org/10.1111/j.1463-5224.2006.00493.x Publication
Researcher Affiliations
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
MeSH Terms
- Animals
- Animals, Newborn
- Biometry
- Cataract / physiopathology
- Cataract / veterinary
- Cataract Extraction / veterinary
- Cornea / anatomy & histology
- Cornea / diagnostic imaging
- Female
- Horse Diseases / physiopathology
- Horses
- Lenses, Intraocular / veterinary
- Male
- Postoperative Period
- Ultrasonography
Citations
This article has been cited 9 times.- Borriello G, Valentini F, Rampinelli M, Ferrini S, Cagnotti G, D'angelo A, Bellino C. Ocular Ultrasonography in Healthy Calves with Different Transducers. Animals (Basel) 2023 Feb 19;13(4).
- Knickelbein KE, Lassaline ME, Kim S, Scharbrough MS, Thomasy SM. Corneal thickness and anterior chamber depth of the normal adult horse as measured by ultrasound biomicroscopy. Vet Ophthalmol 2022 May;25 Suppl 1(Suppl 1):17-24.
- Abdelbaset-Ismail A, Aref M, Ezzeldein S, Eisa E, Gugjoo MB, Abdelaal A, Emam H, Al Syaad K, Ahmed AE, Alshati A, Abd El Raouf M. Ultrasound, Dacryocystorhinography and Morphological Examination of Normal Eye and Lacrimal Apparatus of the Donkey (Equus asinus). Animals (Basel) 2022 Jan 6;12(2).
- Kawasaki M, Furujo T, Kuroda K, Azuma K, Okamoto Y, Ito N. Characterising keratometry in different dog breeds using an automatic handheld keratometer. Vet Rec 2020 May 2;186(15):e4.
- Slenter IJM, Hermans H, Ensink JM, Willems DS, Veraa S, Grinwis GCM, Boevé MH. Clinical, ultrasonographic, and histopathologic findings in seven horses with Descemet's membrane detachment: A case series. Vet Ophthalmol 2020 Jan;23(1):181-189.
- Meister U, Görig C, Murphy CJ, Haan H, Ohnesorge B, Boevé MH. Intraocular lens power calculation for the equine eye. BMC Vet Res 2018 Apr 3;14(1):123.
- Gialletti R, Marchegiani A, Valeriani T, Nannarone S, Beccati F, Fruganti A, Laus F. A survey of ocular ultrasound abnormalities in horse: 145 cases. J Ultrasound 2018 Mar;21(1):53-59.
- Meister U, Ohnesorge B, Körner D, Boevé MH. Evaluation of ultrasound velocity in enucleated equine aqueous humor, lens and vitreous body. BMC Vet Res 2014 Oct 14;10:250.
- Valentini S, Castagnetti C, Musella V, Spinella G. Assessment of intraocular measurements in neonatal foals and association with gender, laterality, and body weight: a clinical study. PLoS One 2014;9(10):e109491.
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